The invention relates to a stepping mechanism for adjusting a vehicle seat, in particular for adjusting an automobile seat.
DE 44 00 910 A1 discloses a known stepping mechanism which is designed and constructed as a drive for a seat height adjuster, and which enables a pumping motion of a manually actuatable lever symmetrically in both directions of adjustment. As a result, a shaft is driven, which in turn adjusts the seat structure of the vehicle seat by means of gearing. During the pumping motion of the lever, a force is transmitted by means of a pawl, which engages a gear. At the same time, a freewheel is released, which prevents the shaft from rotating back in the blocked direction. When returning the lever from its deflected position to its idle position, the pawl is able to disengage from the gear, and to slide over the teeth of the gear. This disadvantageously results in a disturbing noise, a so-called xe2x80x9crattle.xe2x80x9d
In accordance with one aspect of the present invention, an improved stepping mechanism is provided. The stepping mechanism includes a gear mounted for rotating relative to a housing. The stepping mechanism also includes a pawl that is operative for being pivoted toward and engaged to the gear. The pawl is also operative for rotating the gear while engaged thereto. In addition, the pawl is operative for moving along and relative to the gear. A body of the stepping mechanism is mounted for rotating in response to the rotating of the gear. The stepping mechanism also includes a friction spring that extends at least partially around the body for frictionally engaging the body. The friction spring is operative for releasing the pawl from the gear and keeping the pawl substantially away from the gear while the pawl is moving along and relative to the gear, so that contact between the pawl and the gear is restricted while the pawl is moving along and relative to the gear.
As a result of providing the friction spring, by which the pawl can be released from the gear, it is possible to return the below-discussed manually actuable lever of the stepping mechanism noiselessly, i.e., without the aforesaid xe2x80x9crattle.xe2x80x9d The use of the friction spring is not limited to a stepping mechanism. It may be used in any mechanism in which it is desirable to quietly move toothed surfaces past one another.
Preferably, the body about which the friction spring loops is a step of the gear or a shaft that does not rotate relative to the gear, but that does rotate with the gear, so that the friction spring can be carried along by the gear. It is advantageous and preferred for the friction spring to define a flat curved shape, so that the friction spring is not too sensitive to tolerances. According to one example in which the friction spring defines a flat curve, the friction spring includes radially outward directed bulges and lies in line contact against the step only in intermediate ranges.
In a preferred embodiment, the pawl is movable by a manually actuatable lever that is pivotably mounted. Preferably, the pawl is pivotably connected to a guide bar that is mounted to be capable of pivoting coaxially with the lever. As a result, the pawl is movable at least in part independently of the lever. This independent movability allows the friction spring to raise the pawl. Additionally, the lever has available a mechanism for releasing, for example, a stop. Furthermore, this also presents the possibility of realizing a simple antirotation device. The friction spring may be designed and constructed such that it opens, for example, when entrained by the guide bar, that it closes upon contact with the pawl, and that it is tightened to a certain degree, i.e., it does not move due to frictional interaction with the body about which it loops. Depending on the geometric design of the ends of the friction spring, it may be entrained by the guide bar always at the same end or at the end leading in the direction of rotation. A simple-to-make means for entraining the friction spring includes stops on the pawl and the guide bar, for example in the form of screwed-in pins.
A preferred application of the stepping mechanism according to the invention is a drive for a seat height adjuster, wherein the automobile seat is raised upward in a pumping motion by means of the lever. The downward directed adjustment of the automobile seat occurs by a downward movement, which is released, for example, by the lever. The downward movement may then occur in one step assisted only by the force of weight. In comparison with the state of the art, a greater angular freedom of the lever is available for the upward pumping motion. This allows for the number of the necessary strokes of the lever to be selectively decreased, or for the transmission via the lever to be increased. In the latter instance, a smaller lever force is to be applied, and absorbency relative to crash forces is increased. As a stop, a freewheel is able to prevent an unwanted rotation of a shaft of the drive for the seat height adjuster. If the shaft is caused to rotate due to vibrational loads, the pawl can serve at the same time as an antirotation device.